JavaScript Tutorial

Write getDiscount(total): 20% for 5000+, 10% for 2000+, otherwise 0. Print results for 6000, 2500 and 500.

Print the 7 times table from 7 × 1 to 7 × 10 in the format "7 x 3 = 21".

Write celsiusToF(c) that returns c × 9/5 + 32. Print the result for 0, 37 and 100.

Rewrite function isEven(n) { return n % 2 === 0; } as an arrow function and use it with filter on [1, 2, 3, 4, 5, 6].

Start with [10, 20, 30]. Add 40 at the end and 5 at the start, then print the array, its length and whether it includes 25.

Calculate the average of the numbers [10, 20, 30, 40].

Create a product object with name, price and inStock. Increase the price by 10%, then print all keys and the new price.

Given scores = { asha: 82, ravi: 67, meera: 91 }, print each name with "pass" (≥ 70) or "retry".

Turn the title " Learn JavaScript Fast " into a URL slug: "learn-javascript-fast".

Calculate 18% GST on ₹499 and print the total formatted as Indian rupees.

Calculate how many days remain from 1 March 2026 until 15 August 2026.

Predict the output, then run it: let a = 1; function f() { let a = 2; return a; } console.log(f(), a);

Predict the output: console.log(a); var a = 5; console.log(a);

Write makeMultiplier(factor) that returns a function multiplying its argument by factor. Create double and triple.

Fix this bug so it prints "Counter: 1": const c = { n: 0, inc() { this.n++; console.log('Counter:', this.n); } }; setTimeout(c.inc, 0);

Use bind to create sayHiRavi from introduce so that sayHiRavi('!') prints "Hi, I am Ravi!".

From const product = { title: 'Desk', price: 12000 }, destructure title and price, with a default stock of 0, and print all three.

Merge [1, 2] and [3, 4] into a new array, and write avg(...nums) that returns the average of any numbers.

Build the message "Order #102 for Ravi: 2 × Mouse = ₹1400" from variables orderId, customer, qty, product and price (700).

Add a “Clear list” button that removes every item and resets the heading to “Shopping list (0)”.

Make a character counter: show “12 / 100” under a textarea as the user types.

Add stopPropagation to the inner listener and predict what is logged when clicking the button.

Extend the example: add a “done” button that toggles a line-through style on its item, using the same single listener.

Add a rule that the email must end with "@example.com", with the message “Use your company email”.

Write safeDivide(a, b) that throws a RangeError when b is 0, and call it inside try…catch.

Use Promise.all to load users 1, 2 and 3 in parallel with fetchUser and log all their names.

Rewrite this with async/await: fetchUser(1).then(u => console.log(u.name)).catch(e => console.log(e.message));

Fetch https://jsonplaceholder.typicode.com/todos?_limit=3 and log each todo’s title.

Store { theme: "dark", fontSize: 16 } as a JSON string, parse it back, and print fontSize + 2.

Count how many times the visitor has opened the page and show “Visit #3” on the third visit.

Store the current wizard step (1–3) in sessionStorage and restore it on reload.

Create greet.js exporting a named function hello(name), and import it in app.js to log hello("Asha").

Create a BankAccount class with a private #balance, deposit(amount), withdraw(amount) that refuses overdrafts, and a balance getter.

Create vehicle = { wheels: 4 } and car = Object.create(vehicle) with brand "Tata". Log car.wheels and whether wheels is car’s own property.

Count how many times each letter appears in "banana" using a Map, and print the counts.

Use a WeakSet to make a function process(obj) that only processes each object once.

Write a generator evens() that yields 0, 2, 4, … forever, and log the first five values.

Use debounce to log "Saved!" only once, 500 ms after the last of several rapid calls to save().

Write startClock() that logs the time every second and returns a stop() function that clears the interval.

Render 1,000 <li> elements efficiently into a <ul> using a DocumentFragment.

Write a function escapeHtml(str) that replaces & < > " ' with HTML entities.

Extend the tip calculator with a “Round up per person” checkbox that rounds each share up to the next ₹10.